An introduction to the big factors in energy use and sustainability of one’s home.
(For an overview of where we need to get to in order to be sustainable in the long term on energy, greenhouse gas emissions and land use, see this post)
In terms of the energy and resource use that we have direct control over, our homes make up the biggest portion. Though it of course varies tremendously from person to person, our homes on average account for about half of the energy that we consume directly. Housing has changed immensely in the last hundred or so years, going from drafty and uninsulated places heated primarily by wood, coal or heating oil, and with no electricity or running water, to our current insulated homes with all the modern amenities. All these amenities and comforts use a lot of energy. Energy efficiency across our homes has been improving, it is a slow process. Building standards are requiring better homes every year, but we could be doing so much more, and more quickly. We now have the knowledge to build homes that use only a fraction of the energy that current building codes require. These homes can be more comfortable while having only modestly higher upfront costs. The energy savings are immense and those higher upfront costs are usually recouped through lower energy and maintenance costs. These better built homes could have higher resale value as well. The biggest impediments to building better homes are the inertia of the status quo, and the failure of the real estate market to properly value fundamentals like insulation and air sealing; people tend to see and think about the nice kitchens but not what is behind the walls.
While I encourage you to dig into the ins and outs of home energy use, sustainable materials and greenhouse gas emissions, this is a lot of work that not everyone has the time or temperament for. Thankfully, there are lots of organizations and certifications that do much of the heavy lifting for us. In fact, there are now enough ‘green’, ‘healthy’ and ‘efficient’ certifications that it can be hard to keep track of them all. All of these organizations are seeking to make buildings that cause less pollution, use less energy, and provide higher quality human living space. A non-exhaustive list includes Passive house, LEED, Net Zero Energy, Living Buildings, and every country has its own additional ones; here in Canada there is Energy Star Certification, R-2000, Energuide, Novoclimat, and others. Whenever you deal with architects, contractors and other tradespeople, some will want to work with ‘green’ building and be knowledgeable about it, while others are only willing to do work the ‘standard’ older way.
If you are ever in the market for a new home, or especially if building a custom home, I think that a good target to aspire to is a home that uses 75% less energy than one built to barely meet code minimums. This kind of target can be reached with easily available materials, and can be accomplished by most of the tradespeople that are out there building homes right now. If buying a home in a new development, find out the details about the actual construction of the building envelope, and not just the final finishes. Some builders do immensely better than others in creating well built and well insulated homes.
For improving your current home, while every little bit counts you will usually have a much greater impact by going after a few big things like improving insulation or getting rid of air infiltration (draftiness) rather than trying to change lots of little behaviors (unplugging your phone charger when its not in use, always turning off all the lights). It may require more planning and money upfront, but then the savings will be effortless and continue for the lifetime of the home. The easiest way to get a handle on what to do and the size of impact that improvements could have comes from having a home energy audit performed. A professional inspector comes to your home and evaluates the structure and home systems, and then can give itemized lists of what could be upgraded and how large an effect it would have. Depending on the specifics of your situation, following through on these improvements could reduce your home energy use very significantly, by as much as 50% in some cases.
Heating and cooling:
Just as housing is the biggest portion of a person’s direct energy use, heating and cooling are the largest portion of a home’s energy use. Heating and cooling are two sides of the same coin, working to control the movement of heat to either keep it in or out. Reducing the energy needed for home heating and cooling is one of the biggest ways that a person can reduce their total energy use, and therefore greenhouse gas emissions and other pollution. I’ll go through each of the major factors that affect heating and cooling in turn.
Low surface area to volume is better. A simple cube or dome shaped building is the most energy efficient shape, as there is the least surface facing the temperature extremes of the environment compared to the comfortable ‘room temperature’ that we maintain within. Complicated building shapes or those that are long and thin have much more surface area and, other things being equal, require much more energy to heat and cool. Along the same lines, large buildings are more energy efficient than small buildings. Apartment dwellers, and those in other shared-wall buildings, are at a major energy advantage, because they have fewer sides of the units exposed to the outside air. So in terms of energy efficiency a compact shaped multi-unit building has the biggest advantage for lowering heating and cooling loads.
Smaller is better. This runs a bit counter to the point made above about large multi-unit buildings, but a smaller home requires less conditioning than a large one. The average new home being built today is close to 2500 square feet, vastly larger than the homes of our grandparents. When shopping for homes or considering building a home, taking the time to truly consider your needs may often lead you to a smaller home than many of those available. There is even a movement afoot for building ‘tiny’ homes, though these are very much a niche choice. Look for a home big enough to fit your needs and stop there.
More insulation is better. Insulation is essentially a sweater for your home, preventing heat from passing through the outer surfaces. In general, the thicker the layer of insulation, the less heat passes through it. The majority of homes are built at or near the code-required minimum levels of insulation. Why? Because this is the cheapest way for a builder to get a house up, allowing them to sell it at a lower price. It may be cheap to build, but is expensive to heat and cool. Builders’ incentives don’t line up perfectly with home owners, as owners should also be considering how that home will be to live in for years. If builders were to take into account the heating and cooling bills of a house into account, they would be insulating better. If they were to take total energy and resource use into account, insulation would be even better than that. This is because most of the total energy that a home consumes is from years of use rather than the energy that goes into building the home in the first place. Codes are getting better by the year, but this is one of the biggest places where individuals can have an effect by demanding better than the minimum. The ‘Passive House’ movement creates homes that use only 1/10 as much energy than typical homes for heating and cooling.
More air tight is better. All houses ‘breathe’ to some extent. There are tiny cracks all around a home where air can pass through, at the edges of windows and doors, around electrical and plumbing penetrations, even between the boards that make up the structure. All of this air leaking in and out of a home carries heat, allowing heat to escape all winter and allow in unwanted heat in the summer. Many older homes lose enormous amounts of energy in this way, and can feel very drafty. This draftiness is another one of the main targets in home energy improvements, and it is possible to seal many of these air leaks to drastically improve a home’s performance. With new construction, air infiltration should be eliminated as much as possible. In well-built new homes, they are so tight that they need to have an air exchanger system to bring in fresh air to maintain healthy air quality. These air exchangers (often heat recovery ventilators) allow control over the air going in and out, and can even recover some of the heat that would otherwise be lost. As an architect friend of mine says, “build tight, ventilate right”.
Windows and passive solar management. Windows are very important for daylighting and views, but they don’t make great walls from an insulating perspective. Newer high performance windows have double, triple, or even more panes of glass, but even so these windows do much less to insulate a building than the surrounding walls. Windows also allow a lot of heat into a building when the sun shines through, which can be either a blessing or a curse. On cold winter days we welcome that additional heat, but want to keep it out on hot sunny days. South facing windows can be great for gathering this winter heat when the sun stays low in the sky, and some overhangs or other shade can keep out the heat when the sun is high during the summer. Lots of west-facing windows make a home very prone to overheating from spring through fall from the intense late afternoon sun. One should be strategic about the size and location of windows, as they can have a big impact on a home’s energy use.
Heating and cooling systems. The sustainability impact that the mechanical heating and cooling systems have on a home comes down to a few things including efficiency and fuel source. Some systems are much more efficient than others, generally measured in percent efficiency. The most efficient of all are called heat pumps, and include air conditioners, air source heat pumps, and ground source heat pumps (refrigerators use the same principle as well). These systems don’t produce heat directly, instead they simply move the heat from one location to another, with the effect of making one location warmer and another colder at the same time. So an air conditioner takes heat from your home and moves it outside, and other heat pumps take heat from the outside and move them into your home. The point is that heat pumps can often move about 3 units of heat for each unit of electricity that they use, making them around 300% efficient. Electric heating is usually 100% efficient, taking electricity and using it to heat up metal heating elements. Natural gas and other fossil fuel heating are usually from 60 to 90% efficient, with some of the energy from the fuel going outside with the exhaust. If you are in the market for new heating and cooling systems, make sure to buy a highly efficient unit, and these are often rated with systems like Energy Star ratings. As for which fuel to choose, heat pumps using electricity are usually the most sustainable choice, as electricity can be produced from renewable sources and the heat pumps are so efficient. However, natural gas will remain attractive for a long while as it is currently so inexpensive, and other fuels will continue to be important in certain situations.
Domestic hot water
The second biggest energy user in most homes is the water heater, using on average 20% of the energy in a home. Water holds heat extremely well, so it takes a great deal of energy to heat up water for showers, bathing, washing, etc. The total amount of energy that hot water consumes depends how much water your home uses, and then there are the same heating efficiency and fuel concerns mentioned in the paragraph above. Most homes have either electric or natural gas water tanks, but there are also tankless versions that make water hot on demand, and there are even heat pump water heaters that take their heat from within your home or the air outside. As mentioned for whole home heating and cooling, purchase the most efficient model that you can, and think about transitioning to electric especially as the electricity grid gets more and more ‘green’.
For how much water one uses, there are a lot of things that one can do to reduce hot water (and therefore energy) use, many of which are painless. One can install low flow shower heads and purchase water-efficient clothes and dish washers, and these steps alone could reduce water heating energy by a third or more. Then there are all sorts of behavioral changes, of shorter showers, washing laundry in cold water, running the dishwasher only when it is full, etc. If your family is a ‘typical’ user of hot water, it is entirely possible with these adjustments that you could cut in half the energy your home needs for hot water.
Electrical loads and other home energy use.
As heating and cooling use around 50% of home energy and hot water uses an additional 20%, that leaves around 30% for the rest of a home’s energy use. This includes our lighting, computers, entertainment systems, refrigerators, stoves, clothes dryers, dehumidifiers, and more. There isn’t a single one of these uses that dominates, with cooking, cooling, lighting, cleaning, and electronics all accounting for big slices of this pie, making a given household’s use really dependent on that family’s habits. In order to be as sustainable as possible, the first thing that one should do is to buy the most energy efficient products, and almost all of these have Energy Star, Energuide, or similar rankings and data easily available. For example, a new high efficiency refrigerator uses three to four times less energy than a typical one from 30 years ago. Insulation in refrigerators has improved, as well as all the pumps, compressors and other components. LED lighting uses 85% less electricity than incandescent bulbs of the same brightness. In addition to buying with efficiency in mind, the other thing that one should do is to only have and use those devices that are really worthwhile and to not have a bunch of stuff that you don’t need or that doesn’t actually improve your life.
The other side of the sustainability of home electricity use is where that energy comes from. While some of the heating appliances use natural gas or propane, most of this energy is provided by electricity from your local power utility. An individual has relatively little control over the utility, but pressure from advocacy groups certainly does influence utilities, and there are programs in many places that allow a person to buy renewable energy; the main Canadian one is called Bullfrog Power. The most problematic sources of electricity are fossil fuels, particularly coal. Fossil fuel based electricity releases a massive amount of carbon dioxide and other pollutants into the atmosphere. Other energy sources tend to be much better for the environment. Nuclear power is important in some regions and while it is controversial in some other ways, it doesn’t contribute to global climate change. Renewable sources of electricity are where we need to continue to grow. Hydropower is already an important energy source in much of the world, but the best sites are now mostly in use. Wind and solar are really just coming into their own, and are currently growing exponentially. Wind has a big headstart over solar, but it is likely that solar will catch up to wind in the coming decades. Many sustainability oriented thinkers believe that it will be possible to transition completely to renewable energy with the right infrastructure in place.
The final component of the energy that we use in and around our homes comes from the making of all our stuff and delivering it to us, which is known as embodied energy. Before one has a house or a computer, one has trees, and oil, and mines, and these raw materials need to be collected, refined, and turned into products and shipped out. One can add up all the energy that is needed to do all of this work, and the total is the embodied energy of that product. Take a new house. You first need to pay attention to what the raw materials are, which include trees, metal ores that must be mined, stone used to make concrete, etc. Harvesting and extracting these raw materials has costs, and some materials are much more sustainable than others. Generally, one wants materials that are inexpensive, don’t take a lot of energy to transform, that don’t have toxic or negative byproducts when used, and don’t have a negative impact on land use. Going into the ins and outs of which materials are better or worse is beyond the scope of this particular article, but for one brief example, wood products that come from well-managed forests tend to be some of the most sustainable materials.
For a house, it turns out that the amount of energy needed to build it is something like 10 times as much as it takes to do all of the heating, cooling and electric loads mentioned above for a year. Since a typical home will last for something like 100 years, this means that over the lifetime of the home, 10% of the energy used was to build it, and 90% of the energy will be used to power the day to day use. When you look at it from this perspective, putting in some extra insulation when building a new home in order to cut the home energy use by half starts to seem like an amazing deal.
Embodied energy can be calculated for all of the other stuff that we have in our homes too. Each product takes raw materials and energy to make, and each one lasts only so many years before it falls apart, breaks, or becomes obsolete. The takeaway for sustainable living is to do one’s best to buy products that have less embodied energy, which may include those that are smaller, simpler, less transformed from their raw materials, coming from more sustainable raw materials, are more easily recycled, and those that last a much longer time. Buying quality goods means that you won’t have to replace that particular item for a much longer time.
Getting more information
If you want to get more serious about digging into the specifics of sustainability and housing, there are some other articles here on Sunshine Saved, and some of the organizations mentioned above have a lot of resources. We’ll end with the links to a few other sites that are dedicated to better homes and open the door to thousands of pages from all sorts of experts on these topics. A starting list to take you a next step down the road to sustainability includes Green Building Advisor, Fine Homebuilding, the Building Science Corporation, Ecohome, and Inhabitat.